Light-emitting device containing a composite electroplated substrate

ABSTRACT

The application is related to a method of forming a substrate of a light-emitting diode by composite electroplating. The application illustrates a light-emitting diode comprising the following elements: a light-emitting epitaxy structure, a reflective layer disposed on the light-emitting epitaxy structure, a seed layer disposed on the reflective layer, a composite electroplating substrate disposed on the seed layer by composite electroplating, and a protection layer disposed on the composite electroplating substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the right of priority based on Taiwan PatentApplication No. 097129481 entitled “A Light-Emitting Device Containing aComposite Electroplated Substrate”, filed on Aug. 1, 2008, which isincorporated herein by reference and assigned to the assignee herein.

TECHNICAL FIELD

The present application generally relates to a light-emitting device,and more particularly to a light-emitting diode comprising a compositeelectroplated substrate.

BACKGROUND

The vertical type light-emitting diodes (LEDs) become a popular choiceto light-emitting diodes package for its simple design, high power, highefficiency, and long life-time. To optimize the heat dispersion, thelight-emitting diodes are usually attached to the metal substrate bybonding technology, or by electroplating technology to evaporate metalfilm on the epitaxy layers. However, due to the difference of thethermal expansion coefficients of materials, the light-emitting diodewafer often cracks during the manufacturing which influences the waferlife-time indirectly.

Generally, a metal matrix composite material is produced by fusingmaterials having low thermal expansion coefficient with metals havinghigh thermal conductivity in a high temperature process to achieve highthermal conductivity and low thermal expansion coefficient. However, thehigh temperature process does not suit for light-emitting diode chipmanufacturing. Recently, the composite electroplating has developedvigorously. The various kinds of composite material compositions havebeen developed and used in the surface coating for the purpose ofwear-resisting and waterproof. Taking the nickel-silicon carbidecomposite electroplating as an example, the principle is to precipitateand co-coat nickel and silicon carbide on the substrate by theelectroplating solution containing the nickel ions with the inertsilicon carbide particles suspended therein. When there is stressexisted between the composite electroplating layer and the substrate,the material(s) selection of the interfacial layer, the number oflayers, and the thickness of each layer are important topics forconsidering.

SUMMARY

In one embodiment of the present application, a light-emitting diodeincludes a light-emitting epitaxy structure, a reflective layer on thelight-emitting epitaxy structure, a seed layer on the reflective layer,a composite electroplating substrate on the seed layer, and a protectionlayer on the composite electroplating substrate.

In one embodiment of the present application, a light-emitting diodefurther includes an interfacial layer between the seed layer and thecomposite electroplating substrate.

In one embodiment of the present application, a light-emitting diodefurther includes an intermediate layer between the reflective layer andthe seed layer.

In one embodiment of the present application, a light-emitting diodefurther includes a multiple-film layer stacked alternately by multiplehigh strength films and multiple high toughness films between thereflective layer and the seed layer.

In one embodiment of the present application, a light-emitting diodecomprises an interfacial layer wherein the material of the interfaciallayer can be copper, gold, or nickel.

In one embodiment of the present application, a light-emitting diodecomprises a reflective layer wherein the material of the reflectivelayer can be as a stack of titanium/aluminum, titanium/gold, ortitanium/silver.

In one embodiment of the present application, a light-emitting diodecomprises a seed layer wherein the material of the seed layer can be asa stack of titanium/gold, titanium/copper, chromium/gold, orchromium/platinum/gold.

In one embodiment of the present application, a light-emitting diodecomprises a composite electroplating substrate is formed by thecomposite electroplating method wherein the material of the compositeelectroplating substrate can be copper-diamond, copper-silicon carbide,nickel-silicon carbide, carbon nanotube-nickel, carbon nanotube-copper,or carbon nanofiber-copper.

In one embodiment of the present application, a light-emitting diodecomprises a protection layer wherein the material of the protectionlayer can be gold or nickel.

In one embodiment of the present application, a light-emitting diodecomprises an intermediate layer wherein the material of the intermediatelayer can be nickel, nickel cobalt, copper tungsten, copper molybdenum,nickel phosphorus alloy, or nickel ion alloy.

In one embodiment of the present application, a light-emitting diodecomprises a multiple-film layer stacked alternately by multiple highstrength films and multiple high toughness films, wherein the materialof the multiple-film layer can be as a stack of aluminumnitride/aluminum, aluminum nitride/copper, or titaniumtungsten/aluminum.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIGS. 1A-1F illustrate a process flow of forming a light-emitting diodein accordance with one embodiment of the present application;

FIGS. 2A-2B illustrate a process flow of forming a light-emitting diodein accordance with another embodiment of the present application;

FIGS. 3A-3B illustrate a process flow of forming a light-emitting diodein accordance with further another embodiment of the presentapplication.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first embodiment of the present application is illustrated in FIG.1A to FIG. 1F. Referring to FIG. 1A, a growth substrate 101 is provided.A semiconductor epitaxy structure 105 is formed on the growth substrate,included at least a first conductivity type semiconductor layer 102, anactive layer 103, and a second conductivity type semiconductor layer104. In this embodiment, the first conductivity type semiconductor layer102 is an n-GaN layer, the active layer 103 is an InGaN/GaN multiplequantum wells structure, and the second conductivity type semiconductorlayer 104 is a p-GaN layer. The semiconductor epitaxy structure 105 isformed on sapphire by the epitaxy technology. The reflective layer 106is formed on the semiconductor epitaxy structure 105 as a stack oftitanium (thickness is 30 nm)/aluminum (thickness is 200 nm). It canalso be as a stack of titanium/gold or titanium/silver.

Referring to FIG. 1B, a seed layer 107 is formed on the reflective layer106 to form a stack of titanium (thickness is 30 nm)/gold (thickness is200 nm). It can also be as a stack of titanium/copper, chromium/gold, orchromium/platinum/gold. Referring to FIG. 1C, an intermediate layer 108is formed on the seed layer 107, and can be composed of copper with athickness of 3-5 μm in this embodiment. The intermediate layer can be asingle layer or multiple layers structure. It also can be composed ofgold or nickel. The above-mentioned structure is disposed in the copperion electroplating solution with diamond powder suspended therein toperform a composite electroplating process. A composite electroplatingsubstrate 109 is then formed by the copper and the diamond precipitatingon the intermediate layer, as shown in FIG. 1D. The compositeelectroplating substrate can be a single layer or multiple layersstructure. The material of the composite electroplating substrate canalso be copper-silicon carbide, nickel-silicon carbide, carbonnanotube-nickel, carbon nanotube-copper, or carbon nano fiber-copper.

The protection layer 110 is formed on the composite electroplatingsubstrate because the diamond particles can influence the coating layersurface coarseness and oxidize copper greatly. The protection layer canbe a single layer or multiple layers structure. The material of theprotection layer can be gold or nickel, as shown in FIG. 1E. Finally,the growth substrate 101 is removed, and the light-emitting diodestructure with composite electroplated substrate is formed as shown inFIG. 1F.

An intermediate layer 111 or a high strength and high toughnessmultiple-film layer 112 is formed on the reflective layer 106 if thedifference of the thermal expansion coefficient between thesemiconductor epitaxy structure 105 and the composite electroplatingsubstrate 109 is large, then the composite electroplating process isproceeded. Referring to FIG. 2A, the intermediate layer 111 is apatterned structure and composed of the material(s) with low thermalexpansion coefficient, they can be nickel, nickel cobalt alloy, nickelphosphorous alloy, nickel ion alloy, copper tungsten alloy, or coppermolybdenum alloy. The intermediate layer can be a single layer ormultiple layers structure. The following steps are the same as FIG. 1Bto FIG. 1F to form the light-emitting diode structure 200 as shown inFIG. 2B. Referring to FIG. 3A, the purpose of forming the high strengthand high toughness multiple-film layer 112 on the reflective layer 106is to release the stress and to protect the semiconductor epitaxystructure when the difference of the thermal expansion coefficientbetween the semiconductor epitaxy structure 105 and the compositeelectroplating substrate 109 is large. The high strength and hightoughness multiple-film layer is stacked alternately by the multiplehard films and the multiple soft films, and the material of themultiple-film layer be as a stack of aluminum nitride/aluminum, aluminumnitride/copper, or titanium tungsten/aluminum. The number of stackedlayers and the thickness of each layer can be adjusted for productperformance concerns. The following steps are the same as FIG. 1B toFIG. 1F to form the light-emitting diode structure 300 as shown in FIG.3B.

Other embodiments of the application will be apparent to those skilledin the art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1. A light-emitting diode, comprising: a composite electroplatingsubstrate having a first surface and a second surface; an interfaciallayer on the first surface of the composite electroplating substrate; aseed layer on the interfacial layer; a reflective layer on the seedlayer; and a semiconductor epitaxy structure on the reflective layer,comprising a first conductivity type semiconductor layer, an activelayer, and a second conductivity type semiconductor layer.
 2. Thelight-emitting diode according to claim 1, further including aprotection layer on the second surface of the composite electroplatingsubstrate.
 3. The light-emitting diode according to claim 1, furtherincluding an intermediate layer between the reflective layer and theseed layer.
 4. The light-emitting diode according to claim 3, whereinthe intermediate layer is a patterned structure.
 5. The light-emittingdiode according to claim 1, further including a multiple-film layerbetween the reflective layer and the seed layer.
 6. The light-emittingdiode according to claim 1, wherein the material of the compositeelectroplating substrate can be copper-diamond, copper-silicon carbide,nickel-silicon carbide, carbon nanotube-nickel, carbon nanotube-copper,or carbon nano fiber-copper.
 7. The light-emitting diode according toclaim 1, wherein the composite electroplating substrate is formed by thecomposite electroplating method.
 8. The light-emitting diode accordingto claim 1, wherein the material of the interfacial layer can be copper,gold, nickel, or tin.
 9. The light-emitting diode according to claim 1,wherein the seed layer can be a stack of titanium/gold, titanium/copper,chromium/gold, or chromium/platinum/gold.
 10. The light-emitting diodeaccording to claim 1, wherein the reflective layer can be a stack oftitanium/aluminum, titanium/gold, or titanium/silver.
 11. Thelight-emitting diode according to claim 1, wherein the firstconductivity type semiconductor layer is n-type semiconductor containingat least one or more elements selected from the group consisting ofgallium and nitrogen, and the second conductivity type semiconductorlayer is p-type semiconductor containing at least one or more elementsselected from the group consisting of gallium and nitrogen.
 12. Thelight-emitting diode according to claim 1, wherein the firstconductivity type semiconductor layer is n-type semiconductor containingat least one or more elements selected from the group consisting ofaluminum, gallium, indium, and phosphorous, and the second conductivitytype semiconductor layer is p-type semiconductor containing at least oneor more elements selected from the group consisting of aluminum,gallium, indium, and phosphorous.
 13. The light-emitting diode accordingto claim 2, wherein the material of the protection layer can be gold ornickel.
 14. The light-emitting diode according to claim 3, wherein theintermediate layer is a patterned structure comprising a low thermalexpansion coefficient material.
 15. The light-emitting diode accordingto claim 14, wherein the material of the intermediate layer can benickel, nickel cobalt alloy, nickel phosphorus alloy, nickel ion alloy,copper tungsten alloy, or copper molybdenum alloy.
 16. Thelight-emitting diode according to claim 5, wherein the multiple-filmlayer is stacked alternately by multiple high strength films andmultiple high toughness films.
 17. The light-emitting diode according toclaim 16, wherein the material of the multiple-film layer can be a stackof aluminum nitride/aluminum, aluminum nitride/copper, or titaniumtungsten/aluminum.